Mean Genetic Distance Research Articles

A study of genetic diversity of sesame (Sesamum indicum L.) in Vietnam and Cambodia estimated by RAPD markers

Sesame (Sesamum indicum L.) is a traditional oil crop cultivated throughout South East Asia. To estimate the genetic diversity of this crop in parts at the region, 22 sesame accessions collected in Vietnam and Cambodia were analyzed using 10 RAPD markers. The 10 primers generated 107 amplification products of which 88 were polymorphic fragments (83%). Genetic diversity of all populations was Ht = 0.34 when estimated by Nei’s genetic diversity and species diversity was H′sp = 0.513 when estimated by Shannon diversity index. Genetic distance ranged from 0.03 to 0.43, with a mean genetic distance of 0.23. The unweighted pair group method with arithmetic averages (UPGMA) cluster analysis for the 22 accessions divided the material in four groups. The dendrogram revealed a clear division among the sesame accessions based on their geographical region. Interestingly, some geographically distant accessions clustered in the same group, which might indicate the human factor involved in the spreading of sesame varieties. The high level of polymorphism shown suggests that RAPD techniques can also be useful for the selection of parents in sesame (Sesamum indicum L.) breeding program and for cultivar differentiation.

Genetic divergence and phylogenetic analysis of genus Jatropha based on nuclear ribosomal DNA ITS sequence

The genus Jatropha belongs to the family Euphorbiaceae having significant economic importance. The present investigation was undertaken with an aim to understand phylogenetic relationships among seven species (J. curcas, J. glandulifera, J. gossypifolia, J. integerrima, J. multifida, J. podagrica, and J. tanjorensis.) which are widely distributed in India, using nuclear ribosomal DNA ITS sequence (nrDNA ITS) and to compare the results with multilocus marker analysis systems reported earlier for the same genus. The size variation obtained among sequenced nrDNA ITS regions was narrow and ranged from 647 to 654 bp. The overall mean genetic distance (GD) of genus Jatropha was found to be 0.385. Highest interspecific GD (0.419) was found between J. glandulifera and J. multifida. The least interspecific GD (0.085) was found between J. gossypifolia and J. tanjorensis. The highest intraspecific GD was observed in J. podagrica (0.011) and least in J. gossypifolia (0.002). The phylogram obtained using nrDNA ITS sequence showed congruence with the phylograms obtained using multilocus markers system reported earlier with minor variations. The present study also strongly supports high phylogenetic closeness of J. curcas and J. integerrima. The only exception found was J. podagrica which clustered with J. multifida in earlier based on multilocus marker analysis, was clustered with J. curcas in the present analysis. The sequence data generated in the present investigation will help for further studies in intraspecies population, and their phylogenetic analysis, biogeographical, molecular evolution studies and also pave way for future phylogenetic and/or evolution studies among the other groups belongs to the family Euphorbiaceae.

Hepatitis B virus genotype E variability in Africa

Background In sub-Saharan Africa, genotype E is the predominant genotype throughout a vast region spanning from Senegal to Namibia and extending to the Central African Republic in the East. Despite its wide geographic distribution and the high prevalence throughout this genotype E crescent, this genotype has a very low genetic diversity. Objectives Here we review our current understanding of genotype E reanalysing all currently available sequences of the S gene and the complete genome. Results Phylogenetic analysis of the complete genome sequences confirmed a previously suggested South-West/Central African cluster and several lineages of West African sequences. The overall mean genetic distance was 1.71%, with the more Southern countries of the genotype E crescent exhibiting lower distances than the Northern countries. Conclusions Genotype E seems to have a longer natural history in the Northern part of the genotype E crescent than in the Southern countries. As genotype E is essentially absent from the Americas despite the Afro-American slave trade until at least the beginning of the 19th century, genotype E strains may have been introduced into the general African population only within the past 200 years. How the virus may have spread throughout the genotype E crescent warrants further investigation.

Strong genetic impoverishment from the centre of distribution in southern Europe to peripheral Baltic and isolated Scandinavian populations of the pearly heath butterfly

AbstractAim Climatic changes and fluctuations in the past have strongly influenced the distribution of animal and plant species. Such fluctuations are also reflected in the patterns of genetic diversity on both local and global scales. The genetic pattern of the pearly heath butterfly,Coenonympha arcania, was used to evaluate the genetic differentiation of isolated (in north‐western Europe), peripheral (in north‐eastern Europe) and central (in southern Europe) populations in the context of post‐glacial distributional changes of the species.Location Europe (Sweden, Germany, the Baltic states, Italy, Slovenia, Hungary, Romania, Bulgaria). Thus, samples were collected from large parts of the species’ distribution representing the three categories mentioned above.Methods We analysed 18 loci of 569 individuals from 28 populations by allozyme electrophoresis. We used both individual‐based and population‐based analyses, includingF‐statistics, various clustering methods and Markov chain Monte Carlo simulations.Results All loci, exceptFum, were polymorphic. The meanFSTfor all samples was 0.18. The mean genetic distance among populations was 0.046. Two major genetic lineages were distinguished. Populations from the centre of the distributional range in southern Europe and the northern periphery of the distributional range differed significantly in their level of genetic variability. The central populations of south‐eastern Europe showed high levels of genetic diversity and no differentiation among populations.Main conclusions Most probably the two major genetic lineages evolved during glacial isolation in two disjunct Mediterranean refugia. The lack of genetic differentiation across south‐eastern Europe implies a continuous Würm ice age distribution in this area, thus supporting the functional existence of steppe forests throughout this region. The peripheral‐isolated populations in Sweden seem to have suffered from one or more severe bottlenecks, resulting in substantial genetic impoverishment. The peripheral‐connected eastern Baltic populations, on the other hand, are affected by post‐glacial and possibly recurrent gene flow from more central parts of the distribution.

The remarkable species complex Mimagoniates microlepis (Characiformes: Glandulocaudinae) from the Southern Atlantic Rain forest (Brazil) as revealed by molecular systematic and population genetic analyses

The aim of the present study is to test by molecular DNA data a hypothesis concerned to speciation by allopatry occurring in Mimagoniates microlepis, associated to the Serra do Mar mountain chain (Atlantic Rain Forest hotspot) in Southern Brazil. Overall genetic diversity and mean genetic distances were high, demonstrating both good conservation status and genetic differentiation. Neighbor-Joining (NJ) and parsimony analyses, together with population genetic parameters (ΦST, Nm, GST, and AMOVA), identified two main vicariant genetic/evolutionary stocks dividing the upper Iguacu River samples from those of the coastal plains. Other well-supported intrinsic monophyletic clades were also identified, suggesting fast and remarkable speciation processes. In addition, the genetic, evolutionary, geographic, and phylogeographic evidences reinforced an occurring species complex. Moreover, these evolutionarily significant units (species complex) seem to be inside four natural biogeographic areas. Thus, the genesis and evolution of the Serra do Mar complex might be associated to diversification processes of M. microlepis. Such a consideration suggests that the areas including the upper Iguacu River and the coastal plains of the states of Sao Paulo, Parana, and Santa Catarina require distinct conservation policies involving one of the global biodiversity hotspots, namely, the Brazilian Atlantic Rain Forest.

Genetic Diversity of Maize Populations Developed by Two Kinds of Recurrent Selection Methods Investigated with SSR Markers

Two cycles of biparental mass selection (MS) and one cycle of half-sib-S3 family combining selection (HS-S3) for yield were carried out in 2 synthetic maize populations P 4C 0 and P 5C 0 synchronously. The genetic diversity of 8 maize populations, including both the basic populations and their developed populations, were evaluated by 30 SSR primers. On the 30 SSR loci, a total of 184 alleles had been detected in these populations. At each locus, the number of alleles varied from 2 to 14, with an average of 6.13. The number and ratio of polymorphic loci in both the basic populations were higher than those of their developed populations, respectively. There was nearly no difference after MS but decreased after HS-S3 in both the basic populations in the mean gene heterozygosity. The mean genetic distance changed slightly after MS but decreased in a bigger degree after HS-S3 in both the basic populations. Analyses on the distribution of genetic distances showed that the ranges of the genetic distance were wider after MS and most of the genetic distances in populations developed by HS-S3 were smaller than those in both the basic populations. The number of genotypes increased after MS but decreased after HS-S3 in both the basic populations. The genetic diversity of intra-population was much more than genetic diversity of inter-population in both the basic populations. All these indexes demonstrated that the genetic diversity of populations after MS was similar to their basic populations, and the genetic diversity was maintained during MS, whereas the genetic diversity of populations decreased after HS-S3. This result indicated that heterogeneity between some of the individuals in the developed populations increased after MS, whereas the populations become more homozygotic after HS-S3.

The genetic structure of the mountain forest butterfly Erebia euryale unravels the late Pleistocene and postglacial history of the mountain coniferous forest biome in Europe

The distribution of the mountain coniferous forest biome in Europe throughout time is not sufficiently understood. One character species of this habitat type is the large ringlet, Erebia euryale well reflecting the extension of this biome today, and the genetic differentiation of this species among and within mountain systems may unravel the late Pleistocene history of this habitat type. We therefore analysed the allozyme pattern of 381 E. euryale individuals from 11 populations in four different European mountain systems (Pyrenees, Alps, Carpathians, Rila). All loci analysed were polymorphic. The mean F(ST) over all samples was high (20%). Furthermore, the mean genetic distance among samples was quite high (0.049). We found four different groups well supported by cluster analyses, bootstraps and hierarchical variance analyses: Pyrenees, western Alps, eastern Alps and southeastern Europe (Carpathians and Rila). The genetic diversity of the populations was highest in the southeastern European group and stepwise decreased westwards. Interestingly, the populations from Bulgaria and Romania were almost identical; therefore, we assume that they were not separated by the Danube Valley, at least during the last ice age. On the contrary, the differentiation among the three western Alps populations was considerable. For all these reasons, we assume that (i) the most important refugial area for the coniferous mountain forest biome in Europe has been located in southeastern Europe including at least parts of the Carpathians and the Bulgarian mountains; (ii) important refugial areas for this biome existed at the southeastern edge of the Alps; (iii) fragments of this habitat types survived along the southwestern Alps, but in a more scattered distribution; and (iv) relatively small relicts have persisted somewhere at the foothills of the Pyrenees.

Genetic Differentiation of the Fejervarya limnocharis Complex from Bangladesh and Other Asian Countries Elucidated by Allozyme Analyses

The present study was conducted to elucidate the genetic divergence and the phylogenetic relationships in the F. limnocharis complex from Bangladesh and other Asian countries such as Sri Lanka, Thailand, Malaysia, Taiwan and Japan by allozyme analyses. We used a total of 95 frogs of the F. limnocharis complex from these countries and F. cancrivora from the Philippines as an outgroup. Based on body size, the F. limnocharis complex from Bangladesh was divided into three distinct groups: large, medium and small types. Allozyme analyses were carried out with 28 loci encoding 20 enzymes and two blood proteins by horizontal starch-gel electrophoresis. When genetic distance was calculated, distinct divergence was found among the three types: mean genetic distance was 0.782 between the small and medium types, 1.458 between the large and medium types, and 1.520 between the large and small types. Phylogenetic trees based on genetic distance showed that all populations of Bangladesh small type strongly formed a cluster and were found to be most closely related to the Sri Lanka population; that all populations of Bangladesh large type formed a very strong cluster and were grouped with several populations from Thailand, Malaysia, Japan, and Taiwan; and that the medium type was segregated from all other groups. This may imply that each of the three types is a different species, and that the medium type is possibly an undescribed taxon.

Genetic relationships and species authentication of Boesenbergia (Zingiberaceae) in Thailand based on AFLP and SSCP analyses

Genetic relationships of 15 Boesenbergia species were examined using AFLP analysis. A total of 893 fragments were generated from six primer combinations; of these, 99.78% were polymorphic. The mean genetic distance between pairs of taxa ranged from 0.435 to 0.935. The neighbor-joining tree resolved investigated species into two separate lineages (corresponding to species possessing compact or elongated inflorescences) and suggests a rapid radiation in Boesenbergia. In addition, SSCP patterns of the partial psbA– trnH spacer were not overlapping between different species and therefore can be used for authentication of Boesenbergia species. Morphologically similar Boesenbergia longiflora and Boesenbergia sp., which showed three SNPs based on psbA– trnH polymorphism were successfully differentiated by SSCP. Moreover, Boesenbergia curtisii displayed intraspecific ecomorphological variation but exhibited the same SSCP pattern. Therefore, AFLP and SSCP are rapid and cost-effective methods for analysis of genetic similarity and species identification in Boesenbergia.

Levels and patterns of allozyme variation in some European larch (Larix decidua) populations

Levels and patterns of electrophoretically detectable variation in 11 enzymes encoded by 18 loci were estimated in eleven populations of European larch (Larix decidua Mill.) from the natural range of the species in Europe. Like other conifers, European larch exhibits a relatively large amount of genetic variability and little differentiation among populations. On the average, 36 % of the loci per population were polymorphic, the average and effective number of alleles per locus were 1.9 and 1.19, respectively, and the expected heterozygosity was 0.157. Only 4 % of the observed genetic variation appeared to be interpopulational, the remainder was due to differences among individuals within populations. The mean genetic distance over all pairs of European larch was 0.008. There was no statistically significant relationship between genetic and geographic distance.

The biochemical systematics of red and sika deer (genus Cervus) in Ireland

Twenty enzyme loci were investigated using starch gel electrophoresis in managed populations of red deer (Cervus elaphus) and sika deer (C. nippon) from Ireland. The red deer, which originated from several European countries, were polymorphic (%P) at 25% of the loci examined and exhibited a mean heterozygosity (H) of 0.025. The sika, originally from Japan, were introduced to Ireland in very limited numbers. Here, %P was 5% and H was 0.006. Mean genetic distance (D) between these taxa was 0.160. Because Scottish red deer, the source of much of the Irish herd, had previously been investigated for 16 of the same enzyme loci, it was possible to merge the present data with results from that earlier study, which also included North American wapiti (C. elaphus canadensis). The resulting phenogram based on genetic distance demonstrates that sika are twice as distantly related to red deer and wapiti, than the latter are to each other and suggests that sika-like forms are ancestral. Also, the demonstration of absolute mobility differences in the products of two enzyme loci in red deer and sika has many practical applications.

Restriction fragment variation of the mitochondrial gene of cytochrome b in some taxa of the Eelpout Family (Pisces, Perciformes, Zoarcidae) from the northern Sea of Okhotsk

The first analysis of restriction fragment length polymorphism (RFLP) of the mitochondrial gene of cytochrome b of fish from the Eelpout Family (Zoarcidae) from the northern Sea of Okhotsk has been performed. The mean genetic distances between the subfamilies Zoarcinae and Lycodinae, subfamilies Lycodinae and Gymnelinae, and subfamilies Zoarcinae and Gymnelinae are 11.14, 13.87, and 14%, respectively. Species of the genus Lycodes (Lycodinae) are characterized by a mtDNA small divergence (on average, 2.04%) and are divided into two groups on the basis of lateral line morphology. Magadania skopetsi, an endemic of Tauiskaya Bay of the Sea of Okhotsk, is genetically close to Hadropareia middendorffii from the same subfamily (Gymnelinae). The mtDNA sequences of species from the genus Lycogrammoides (Lycodinae) differ by 3.83%. The genetic differences between the eelpout Zoarces elongatus Zoarces sp. (d = 4.54%) suggest that the latter is a separate species.

Estimativa da diversidade genética de germoplasma de cebola via descritores morfológicos, agronômicos e bioquímicos

A divergência genética de 64 acessos de cebola (Allium cepa L.) tropicais e subtropicais do banco de germoplasma da Embrapa Hortaliças foi avaliada utilizando 23 descritores morfológicos, bioquímicos e agronômicos. A distância generalizada de Mahalanobis (D²) foi usada como medida de dissimilaridade e os métodos de otimização de Tocher e hierárquico do Vizinho mais Próximo foram empregados para o agrupamento dos acessos. O germoplasma de cebola avaliado apresentou base genética relativamente ampla. As cultivares EX 3000 e Régia foram os acessos geneticamente mais similares. A maior distância genética estimada foi entre os acessos VAL 14 e Beta Cristal. O método de otimização de Tocher proporcionou a formação de treze grupos, enquanto o procedimento hierárquico do vizinho mais próximo possibilitou a formação de doze grupos (corte com 43% de dissimilaridade) A maioria dos acessos dos tipos Grano e Granex, agronomicamente considerados de dias curtos e com ciclo de maturação precoce, se concentraram em mesmo grupo de similaridade genética. À exceção do acesso Tampico White, os demais acessos de bulbos brancos do tipo indústria (Beta Cristal; Dehydrator # 8; Dehydrator # 6; Primero e White Creole) exibiram estreito relacionamento. Os acessos TX 24, Baia Periforme Super Precoce, EX 3001, Excel, Red Creole, H 688, Franciscana IPA 10 e Roxa IPA 3 exibiram alta dissimilaridade genética. Os caracteres teor de açúcares totais, comprimento de bulbo, número de dias para a colheita, porcentagem de bulbos com diâmetro entre 70 e 90 mm e massa média de bulbos foram responsáveis por 58% de toda a variabilidade genética observada entre os acessos. O estudo da divergência entre acessos é importante subsídio na escolha de parentais divergentes e complementares a fim de desenvolver populações segregantes com ampla base genética em programas de melhoramento genético de cebolas tropicais.

Genetic diversity and relationships between nine species of bamboo in Sri Lanka, using Random Amplified Polymorphic DNA

Random Amplified Polymorphic DNA (RAPD) showed a high degree of polymorphism in nine species of bamboo, Dendrocalamus giganteus Wall ex Munro, D. asper Becker ex K. Heyn, D. longispathus (Kurz) Kurz, Bambusa vulgaris `Striata', B. ventricosa, B. bambos (L.) A. Voss, B. atra Lindley, Gigantochloa atroviolacea Wdjaja and Arundinaria hindsii, in Sri Lanka. The lowest mean genetic distance of 0.143 was between B. vulgaris and B. ventricosa. They could however be distinguished morphologically. The genetic distances separating D. longispathus from D. giganteus and D. asper were both greater than that between the latter two species, which had a value of 0.313. Although the genetic distances between Bambusa vulgaris, B. ventricosa and B. bambos were relatively small, B. atra separated from them at greater distances. The smaller genetic distances between G. atroviolacea and B. vulgaris, B. ventricosa and B. bambos indicated that G. atroviolacea had a closer affinity to these three Bambusa species than B. atra. A. hindsii with the greatest genetic distances from all other species in the study, was not related to any of them. RAPD analysis was useful in determining the genetic diversity and relationships and in detecting problematic generic assignments.

COI variation in Scandinavian marine species of Tubificoides (Annelida: Clitellata: Tubificidae)

Intra- and interspecific variation in a 658 bp long part of the cytochrome c oxidase subunit 1 (COI) gene of the mitochondrial genome, i.e. a suggested ‘DNA barcode’, was assessed in four north-west European species of the marine tubificid genus Tubificoides: T. benedii, T. amplivasatus, T. heterochaetus and T. kozloffi. Within species mean genetic distance was from 0.10% (T. amplivasatus) to 0.14% (T. benedii), between species from 19.3% to 22.9%. For T. benedii and T. amplivasatus, material collected in two separate areas, The Sound between Denmark and Sweden, and the Koster area about 330 km to the north along the Swedish west coast, showed a geographically random distribution of COI haplotypes, suggesting that each of these two species forms a continuous population in southern Scandinavia. We conclude that the COI gene is suitable as a barcode marker for the secure identification of these species, at least within the area investigated. Tubificoides heterochaetus is reported for the first time from Denmark.

Genetic Heterogeneity of the Blue Swimming Crab (Portunus pelagicus) in Thailand Determined by AFLP Analysis

Genetic diversity and population differentiation of the blue swimming crab (Portunus pelagicus) in Thailand, originating from Ranong and Krabi located in the Andaman Sea (west) and Chanthaburi, Prachuap Khiri Khan, and Suratthani located in the Gulf of Thailand (east), were examined by AFLP analysis. High genetic diversity of P. pelagicus in Thai waters was found (N=72). The four primer combinations generated 227 AFLP fragments, and the percentage of polymorphic bands in each geographic sample was 66.19-94.38%. The mean genetic distance between pairs of samples was 0.1151-0.2440. Geographic heterogeneity analyses using the exact test and FST-based statistics between all pairwise comparisons were statistically significant (P<0.01), indicating a fine-scale level of intraspecific population differentiation of Thai P. pelagicus. The estimated number of migrants per generation (Nem) was 0.26-0.76, suggesting restricted gene flow levels of P. pelagicus in Thai waters.

Rapd variation of late-maturing sorghum [ Sorghum bicolor (L.) Moench] landraces from Ethiopia

A study on the extent and pattern of genetic variability in late-maturing sorghum [Sorghum bicolor(L.) Moench] landraces collected from the Wello and Hararge areas of Ethiopia was conducted using random amplified polymorphic DNA (RAPD) markers for 70 individuals representing 14 populations. Four oligonucleotide primers generated a total of 55 polymorphic bands with 13–19 bands per primer and a mean of 16 bands across the 70 individuals. The value of the Shannon diversity index among the populations (0.26) and between the two regions (0.24) was low to moderate, despite the high degree of polymorphic bands per primer. The mean genetic distance (0.25) between the populations was found to be low. The low genetic variation may be due to the reduced population size of late-maturing sorghum landraces in the two regions of Ethiopia because of farmers’ decisions in the process of planting, managing, harvesting and processing their crops. Partitioning of the genetic variation into variation between and within the population revealed that 92.9% and 7.10% of the variation was found to be between and within the populations, respectively. Cluster analysis of genetic distance estimates further confirmed a low level of differentiation in late-maturing sorghum populations both between and within the regions. The implications of the results for genetic conservation purposes are discussed.

Cryptic differentiation in alpine‐endemic, high‐altitude butterflies reveals down‐slope glacial refugia

The influence of cyclic climate fluctuations and their impact on high-altitude species is still insufficiently understood. We therefore analysed in this study the genetic structure of cold-adapted animals and their coherence with geographical distributions throughout the Late Quaternary. We analysed 588 individuals from 23 populations of the alpine-endemic lesser mountain ringlet, Erebia melampus, by allozyme electrophoresis to detect its intraspecific differentiation. As an outgroup, we added one population of Erebia sudetica inalpina from Grindelwald (Swiss Alps). Seventeen of 18 loci were polymorphic. The mean F(ST) over all samples was 37%. We detected strong differentiation into three lineages with the genetic distances between the two E. melampus groups being larger than between each of the two E. melampus groups and E. sudetica. The mean genetic distance among these three groups was 0.17. These results give evidence for the existence of a species complex within the E. melampus/sudetica group and indicate a discontinuous distribution within this group during at least the last ice age. One of them, E. sudetica inalpina, is found in the northern Alps and most probably had its Würm glacial refugium north of the glaciated Alps. The western E. melampus group might have had a refugium at the southwestern Alps margin, the eastern group in the lower altitudes of the southeastern and/or eastern Alps. In the latter, a further subdivision within this relict area is possible.

Originality of M3S maize population and changes in allele frequencies revealed by SSR markers after two cycles of selfed progeny recurrent selection

Maksimir 3 Synthetic (M3S) maize population was developed at the Faculty of Agriculture University of Zagreb by intercrossing inbred lines, whose origins trace back to several open-pollinated varieties and local populations from different regions of the former Yugoslavia. The population was subjected to two cycles of selfed progeny recurrent selection for grain yield. The objectives of this study were: (i) to determine genetic distances among the parental inbred lines of the M3S population (M3S progenitors), the M3S population before and after two cycles of recurrent selection, and elite inbred lines representing the BSSS and Lancaster heterotic group; and (ii) to examine the effect of two cycles of recurrent selection on allele frequency changes in the population. Nine M3S progenitors, three BSSS lines, and three Lancaster lines were genotyped at 24 SSR loci, out of which nine randomly chosen loci were used for genotyping 96 individuals from both C0 (the M3S population before selection) and from C2 (M3S population after two cycles of selection). A total of 101 alleles were detected across 24 loci in the 15 lines, whereas 83 alleles were found in the nine M3S progenitors. Among the latter 83 alleles 31 were unique, i.e. found only in one of the progenitors. Mean genetic distance among nine M3S progenitors was 0.61 indicating a broad genetic base of the M3S population. High mean genetic distance was found between M3S progenitors and BSSS lines (0.69) and M3S progenitors and Lancaster lines (0.71). This indicates that the M3S population represents a germplasm source unrelated to both the BSSS and Lancaster germplasm. Mean genetic distance between the M3S population and BSSS as well as Lancaster lines decreased slightly after two cycles of recurrent selection suggesting the need to introduce testers from both groups in future selection in the M3S population in order to maintain heterotic complementarity of the M3S population to these groups. A test of selective neutrality identified several non-neutral loci in the population whose allele frequency changes from the C0 to the C2 cannot be explained by genetic drift. The majority of non-neutral alleles, whose frequency increased after two cycles of selection, were present in at least one line from the BSSS or Lancaster heterotic group.

Genetic structure and differentiation of Psathyrostachys huashanica populations detected with RAPD markers

Psathyrostachys huashanica Keng is a perennial grass and belongs to genus Psathyrostachys under Triticeae. sathyrostachys is found in the center of Middle Asia and the Caucasus Mountain, while P. huashanica, a species endemic to China, is only located in Mt. Hua in the Shaanxi province, China. At present, the population of this species is decreasing, and reaching the edge of extinction. Due to the limitation in distribution and the importance as breeding material for germplasm storage, it has been considered as first class among the national protected rare plants. For this reason, the present study is significant in probing plant flora, origin and evolution of Triticeae, and crop breeding. Randomly amplified polymorphic DNA (RAPD) markers were used to analyze the genetic structure and differentiation of P. huashanica populations sampled in three valleys (Huangpu, Xian, and Huashan Valleys) in Mt. Hua. One hundred and twenty-two RAPD fragments were obtained in all 266 individuals with 20 primers with a mean of 6.1 (2–10) fragments per primer. The percentage of polymorphic loci (PPB) was 60.66% in Huangpu Valley, 90.98% in Xian Valley, 95.08% in Huashan Valley, and the total PPB was 95.08%, which indicated a highly genetic variability of P. huashanica. The Shannon’s Information index and G ST were 0.3306 and 0.3263, respectively, indicating that there were more genetic variations within the subpopulations than those among the subpopulations. The gene flow among the subpopulations of P. huashanica (Nm = 1.0322) was much less than that of the common anemophytes (Nm = 5.24). Mean genetic distance is 0.1 571 (range: 0.0022–0.2901). The highest value of genetic distance was found between the subpopulation (hp1) of Huangpu Valley and the highest altitude subpopulation (h8) of Huashan Valley. Correlation analysis detected significant correlation between genetic distance and vertical distance of altitude. Clustering analysis and principal coordinate analysis revealed the genetic differentiation among the populations of P. huashanica. Differentiation mainly occurred between the higher altitude subpopulations and the lower altitude subpopulations, suggesting that altitude might be the major factor that restricted the gene flow between different altitude subpopulations and resulted in differentiation of subpopulations.